Thermally conductive grease

ABSTRACT

The invention relates to thermally conductive greases that may contain carrier oil(s), dispersant(s), and thermally conductive particles, wherein the thermally conductive particles are a mixture of at least three distributions of thermally conductive particles, each of the at least three distributions of thermally conductive particles having an average (D 50 ) particle size which differs from the other average particle sizes by at least a factor of 5

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 11/459,163, filed Jul. 21, 2006, now allowed, which is acontinuation-in-part of U.S. application Ser. No. 11/195,953, filed Aug.3, 2005, abandoned, the disclosures of which are incorporated byreference in their entirety herein.

BACKGROUND

The invention relates to thermal interface materials and their use.

In the computer industry, there is a continual movement to highercomputing power and speed. Microprocessors are being made with smallerand smaller feature sizes to increase calculation speeds. Consequently,power flux is increased and more heat is generated per unit area of themicroprocessor. As the heat output of the microprocessors increases,heat or “thermal management” becomes more of a challenge.

One aspect of thermal management is known in the industry as a “thermalinterface material” or “TIM” whereby such a material is placed between aheat source, such as a microprocessor, and a heat dissipation device tofacilitate the heat transfer. Such TIMs may be in the form of a greaseor a sheet-like material. These thermal interface materials also areused to eliminate any insulating air between the microprocessor and heatdissipation device.

TIMs typically are used to thermally connect a heat source to a heatspreader, that is, a thermally conductive plate larger than the heatsource, in which case they are referred to as TIM Is. TIMs may also beemployed between a heat spreader and a thermal dissipation device suchas a cooling device or a finned heat sink in which case such TIMs arereferred to as TIM IIs. TIMs may be present in one or both locations ina particular installation.

SUMMARY

In one embodiment, the invention provides a thermally conductive greasethat comprises 0 to about 49.5 weight percent of carrier oil, about 0.5to about 25 weight percent of at least one dispersant, and at leastabout 50 weight percent of thermally conductive particles. The thermallyconductive particles comprise a mixture of at least three distributionsof thermally conductive particles, each of the at least threedistributions of thermally conductive particles having an average (D₅₀)particle size which differs from the other distributions by at least afactor of 5.

In another embodiment, the invention provides a method of making athermally conductive grease of the invention that comprises the steps ofproviding carrier oil, dispersant, and thermally conductive particles,and then mixing the carrier oil (if present), dispersant, and thermallyconductive particles together.

In one aspect, the carrier oil (if present) and dispersant are mixedtogether, and the thermally conductive particles are mixed sequentially,finest to largest average particle size into the carrier oil anddispersant mixture. In another aspect, the thermally conductiveparticles are mixed together, and then mixed into the carrier oil (ifpresent) and dispersant mixture. In another aspect, a portion or all ofthe thermally conductive particles are pre-dispersed with a dispersantprior to mixing the thermally conductive particles into the carrier oil(if present) and dispersant mixture.

In another embodiment, the invention provides a microelectronic packagecomprising a substrate, at least one microelectronic heat sourceattached to the substrate, and a thermally conductive grease disclosedin this application on the at least one microelectronic heat source.

In one aspect, the invention provides the above microelectronic packagefurther comprising a heat spreader and thermally conductive greasedisclosed in this application between the microelectronic heat sourceand the heat spreader.

In another aspect, the invention provides a microelectronic packagecomprising a substrate, at least one microelectronic heat sourceattached to the substrate, a heat spreader, and a heat dissipationdevice attached to the heat spreader wherein a thermally conductivegrease disclosed in this application is between the heat spreader andthe heat dissipation device.

In another aspect, the invention provides a microelectronic packagecomprising a substrate, at least one microelectronic heat sourceattached to the substrate, a heat spreader, a thermally conductivegrease disclosed in this application between the microelectronic heatsource and the heat spreader and a heat dissipation device whereinthermally conductive grease is between the heat spreader and the heatdissipation device.

DETAILED DESCRIPTION

As used herein:

“Grease” means a material having a viscosity of greater than 1×10⁴ cps(10 Pa·s) at 1/s shear rate and 20° C. and a viscosity of less than 10⁸cps at 1/sec shear rate and 125° C.

“Thermally conductive grease” means grease having a bulk conductivity ofgreater than 0.05 W/m-K as measured by the test method Bulk ThermalConductivity described below.

All numbers are herein assumed to be modified by the term “about,”unless stated otherwise. The recitation of numerical ranges by endpointsincludes all numbers subsumed within that range (e.g., 1 to 5 includes1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

Thermally conductive greases (TCGs) of the invention may contain one ormore carrier oils. Carrier oil provides the base or matrix for the TCGsof the invention. Useful carrier oils may comprise synthetic oils ormineral oils, or a combination thereof and are typically flowable atambient temperature. Specific examples of useful carrier oils includepolyol esters, epoxides, silicone oils, and polyolefins or a combinationthereof.

Commercially available carrier oils include HATCOL 1106, a polyol esterof dipentaerythritol and short chain fatty acids, and HATCOL 3371, acomplexed polyol ester of trimethylol propane, adipic acid, caprylicacid, and capric acid (both available form Hatco Corporation, Fords,N.J.); and HELOXY 71 an aliphatic epoxy ester resin, available fromHexion Specialty Chemicals, Inc., Houston Tex.

Carrier oil may be present in the TCGs of the invention in an amount offrom 0 to about 49.5 weight percent, and in other embodiments, from 0 tonot more than about 20 or about 12 weight percent of the totalcomposition. In other embodiments, carrier oil may be present in anamount of at least 2, 1, or 0.5 weight percent of the composition.Carrier oil may also be present in the TCGs of the invention in rangesincluding from about 0.5, 1, or 2 to about 12, 15, or 20 weight percent.

TCGs of the invention contain one or more dispersants. The dispersant(s)may be present in combination with carrier oil, or may be present in theabsence of carrier oil. The dispersants improve the dispersion of thethermally conductive particles (described below) in the carrier oil ifpresent. Useful dispersants may be characterized as polymeric or ionicin nature. Ionic dispersants may be anionic or cationic. In someembodiments, the dispersant may be nonionic. Combinations of dispersantsmay be used, such as, the combination of an ionic and a polymericdispersant.

Examples of useful dispersants include, but not limited to, polyamines,sulfonates, modified polycaprolactones, organic phosphate esters, fattyacids, salts of fatty acids, polyethers, polyesters, and polyols, andinorganic dispersants such as surface-modified inorganic nanoparticles,or any combination thereof.

Commercially available dispersants include those having the tradenamesSOLSPERSE 24000 and SOLSPERSE 39000 hyperdispersants, available fromNoveon, Inc., a subsidiary of Lubrizol Corporation, Cleveland, Ohio;EFKA 4046, a modified polyurethane dispersant, available from EfkaAdditives BV, Heerenveen, The Netherlands; and RHODAFAC RE-610, anorganic phosphate ester, available from Rhone-Poulenc, Plains Road,Granbury, N.J.

Dispersant is present in the TCGs of the invention in an amount of atleast 0.5 and not more than 50 weight percent, and in other embodiments,not more than 25, 10, or 5 weight percent of the total composition. Inanother embodiment, dispersant may be present in an amount of at least 1weight percent. Dispersant may also be present in the TCGs of theinvention in ranges including from about 1 to about 5 weight percent.

TCGs of the invention contain thermally conductive particles. Usefulthermally conductive particles include, but are not limited to, thosemade from or that comprise diamond, polycrystalline diamond, siliconcarbide, alumina, boron nitride (hexagonal or cubic), boron carbide,silica, graphite, amorphous carbon, aluminum nitride, aluminum, zincoxide, nickel, tungsten, silver, and combinations of any of them. Eachof these particles are of a different type.

The thermally conductive particles used in the TCGs of the invention area mixture of at least three distributions of thermally conductiveparticles. Each of the at least three distributions of thermallyconductive particles have an average particle size which differs fromthe average particle size of the distribution above and/or below it byat least a factor of 5, and in other embodiments, at least a factor of7.5, or at least a factor of 10, or greater than 10. For example, amixture of thermally conductive particles may consist of: a smallestparticle distribution having an average particle diameter (D₅₀) of 0.3micrometers; a middle distribution having an average particle diameter(D₅₀) of 3.0 micrometers; and a largest distribution having an averageparticle diameter (D₅₀) of 30 micrometers. Another example may haveaverage diameter particle distributions having average particle diameter(D₅₀) values of 0.03 micrometers, 0.3 micrometers, and 3 micrometers.

The thermally conductive particles used in the TCGs of the invention area mixture of at least three distributions of thermally conductiveparticles resulting in at least a trimodal distribution. In such atrimodal distribution, the minima between the peaks (distance betweenthe baseline of the peaks and the lowest point of the valley betweendistribution peaks) may be no more than 75, 50, 20, 10 or 5 percent ofthe interpolated value (height) between adjacent peaks. In someembodiments, the three size distributions are essentiallynon-overlapping. “Essentially non-overlapping” means that the lowestpoint of the valley is no more than 5% of the interpolated value betweenadjacent peaks. In other embodiments, the three distributions have onlya minimal overlap. “Minimal overlap” means that the lowest point of thevalley is no more than 20% of the interpolated value between adjacentpeaks.

Typically, for a trimodal TCG, the average particle size for thesmallest average diameter may range from about 0.02 to about 5.0micrometers. Typically, the average particle size for the middle averagediameter may range from about 0.10 to about 50.0 micrometers. Typically,the average particle size for the largest average diameter may rangefrom about 0.5 to about 500 micrometers.

In some embodiments, it is desirable to provide a TCG having the maximumpossible volume fraction thermally conductive particles that isconsistent with the desirable physical properties of the resulting TCG,for example, that the TCG conform to the surfaces with which it is incontact and that the TCG be sufficiently flowable to allow easyapplication.

With this in mind, the conductive particle distributions may be selectedin accordance with the following general principles. The distribution ofsmallest diameter particles should have diameters that are smaller than,or nearly bridge, the expected gap between the two substrates to bethermally connected. Indeed, the largest particles may bridge thesmallest gap between substrates. When the particles of the largestdiameter distribution are in contact with each other, a gap or voidvolume between the particles will remain. The mean diameter of themiddle diameter distribution may be advantageously selected to just fitwithin the gap or void between the larger particles. The insertion ofthe middle diameter distribution will create a population of smallergaps or voids between the particles of the largest diameter distributionand the particles of the middle diameter distribution the dimensions ofwhich may be used to select the mean diameter of the smallestdistribution. In a similar fashion, desirable mean particle dimensionsmay be selected for fourth, fifth, or higher order populations ofparticles if desired.

Each distribution of thermally conductive particles may comprise thesame or different thermally conductive particles in each or any of theat least three distributions. Additionally, each distribution ofthermally conductive particles may contain a mixture of different typesof thermally conductive particles

The remaining voids may be thought of as being filled with carrier,dispersant(s) and other components with a slight excess to provideflowability. Further guidance in the selection of suitable particledistributions may be found in “Recursive Packing of Dense ParticleMixtures”, Journal of Materials Science Letters, 21, (2002), pages1249-1251. From the foregoing discussion, it will be seen that the meandiameters of the successive particle size distributions will preferablybe quite distinct and well separated to ensure that they will fit withinthe interstices left by the previously packed particles withoutsignificantly disturbing the packing of the previously packed particles.

The thermally conductive particles may be present in the TCGs of theinvention in an amount of at least 50 percent by weight. In otherembodiments, thermally conductive particles may be present in amounts ofat least 70, 75, 80, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,or 98 weight percent. In other embodiments, thermally conductiveparticles may be present in the TCGs of the invention in an amount ofnot more than 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, or85 weight percent.

The TCGs and TCG compositions of the invention may also optionallyinclude additives such as antiloading agents, antioxidants, levelingagents and solvents (to reduce application viscosity), for example,methylethyl ketone (MEK), methylisobutyl ketone, and esters such asbutyl acetate.

The TCGs of the invention are generally made by blending dispersant andcarrier oil together, and then blending the thermally conductiveparticles sequentially, finest to largest average particle size into thedispersant/carrier oil mixture. The thermally conductive particles mayalso be premixed with one another, and then added to the liquidcomponents. Heat may be added to the mixture in order to reduce theoverall viscosity and aid in reaching a uniformly dispersed mixture. Insome embodiments, it may be desirable to first pretreat or pre-dispersea portion or all of the thermally conductive particles with dispersantprior to mixing the particles into the dispersant/carrier mixture.

The TCGs of the invention may be used in microelectronic packages andmay be used to assist in the dissipation of heat from a heat source, forexample, a microelectronic die or chip to a thermal dissipation device.Microelectronic packages may comprise at least one heat source, forexample, a die mounted on a substrate or stacked die on a substrate, athermally conductive grease of the invention on the heat source, and mayinclude an additional thermal dissipation device in thermal and physicalcontact with the die, such as, for example, a thermal spreader. Athermal spreader may also be a heat source for any subsequent thermaldissipation device. The thermally conductive greases of the inventionare useful to provide thermal contact between said die and thermaldissipation device. Additionally, TCGs of the invention may also be usedin thermal and physical contact between a thermal dissipation device anda cooling device. In another embodiment, the TCGs of the invention maybe used between a heat generating device and a cooling device, that is,without using a heat or thermal spreader in between. TCGs of theinvention are useful in TIM I and TIM II applications.

EXAMPLES Bulk Thermal Conductivity

Bulk thermal conductivity was measured generally in accord with ASTMD-5470-01 on the TCG samples using a Heat Transfer Tester, availablefrom Custom Automation, Inc., Blaine, Minn. The Heat Transfer Tester wasbuilt according to Proposal Number 3M-102204-01 and included suchfeatures as: a vision system capable of measuring parallelism and gapbetween copper meter bars for up to 0.010 inch (0.254 mm) gaps, coppermeter bars with 5 resistance temperature detector (RTD) sensors on eachmeter bar, a cooler to cool the cooled clamping block (to hold thecooled meter bar) having an operating range of from −20 to 100° C. andcan hold the coolant temperature to +/−0.02° C., a 25 lbF load cellmounted on a X-Y micrometer adjust positioning stage, a cooled clampingblock (to hold the cooled meter bar) mounted on the load cell, a heatedclamping block (to hold the heated meter bar) using resistive heatingand has its temperature controlled by a controller and thermocouple, theability to add weights above the heated clamping block to adjust thecontact force on the meter bars from 5 to 50 N, and means to measure andrecord temperature, meter bar gap, and contact force at time intervalsto a spreadsheet.

The vision system used to measure meter bar gap was calibrated asoutlined in the operating procedures provided. The cooler was chargedwith a 50/50 blend of water and ethylene glycol. The gap between thecopper meter bars was set at about 550 micrometers at room temperature.The heater set point was put at 120° C. and the cooler set point at −5°C., and the unit was allowed to equilibrate. The meter bar gap afterequilibration was about 400 micrometers. The surfaces of the hot andcold meter bars were planarized using the individual meter barturnbuckles until the gap between the meter bars read by each of thethree individual cameras fell within a +/−3 μm range.

An excess of each TCG sample tested was placed on the hot meter barsurface and smoothed across the entire face. The head was then closedand clamped into place, causing excess TCG sample to ooze out of themeter bar gap. This excess was removed with a paper towel or a finecloth and the pins of the meter bars were cleaned to facilitate accuratemeasurement of the gap by the three vision cameras. The instrument wasallowed to equilibrate for about 10 minutes as data was continuouslyrecorded. The meter bar gap was lowered about 100 μm and excess TCGsample oozed out of the gap and was cleaned. The instrument was againallowed to equilibrate for about 10 minutes as data was continuouslyrecorded. This sequence of lowering the meter bar gap in about 100 μmincrements, cleaning, and recording data was repeated until a finalreading was taken, typically at a meter bar gap of <100 μm. The meterbars were opened back up to about a 400 μm gap, cleaned, and theprocedure was repeated for the next sample.

The data were recorded every 7-8 seconds by the instrument and containeda time/date stamp, the sample name, the force exerted on the TCG in themeter bar gap, each of the individual meter bar gap readings, and eachof the 10 RTD sensor temperature readings. The file was downloaded intoa spreadsheet for analysis. In the analysis, the last 10 data pointsrecorded at the given gap were averaged, and these averages were usedfor the calculations.

The power flowing through the TCG sample was calculated using the knownbulk conductivity of copper, the dimensions of the copper bars, and thelocations of the RTD temperature sensors. Typically, the calculationsindicated slightly different wattage flowing down the hot meter bar thandown the cold meter bar; these two values were averaged for calculationsextending to the TCG sample. The temperature at the surface of each ofthe meter bars was also extrapolated from a plot of the temperatures andthe RTD sensor locations.

The power, the average of the three individual meter bar gaps, thetemperature drop across the meter bar gap, and the cross sectional areaof the hot/cold meter bars were then used to calculate the temperaturegradient, the power flux, and then the thermal impedance for the TCGsample under those conditions.

These calculations were completed for each of the meter bar gaps atwhich the TCG sample had been tested, and the resulting thermalimpedance and average gap data was plotted. A line was fitted to thedata using spreadsheet software, and the bulk conductivity wascalculated as the inverse of the lines' slope. The y-axis intercept andthe slope were then used to calculate the thermal impedance at a 100 μmmeter bar gap.

Viscosity

The viscosity data on selected samples was generated on a RheometricsRDA3 viscometer (TA Instruments, Newcastle, Del.). The viscometer wasrun with disposable 1 inch (25.4 mm) diameter parallel plates in the logsweep mode starting at 0.5/sec initial shear rate, taking 5points/decade up to 1000/sec shear rate. The gap was set at 0.5 mm for arun, and then lowered to 0.25 mm for a second run on some samples; onother samples the gap was set and run only at 0.25 mm. Temperatures ofthe runs were controlled to either 125° C. or 25° C. as indicated in thetable below. Viscosities were recorded in mPa·s at a 1.25/sec shearrate.

Milling Procedure

Roughly 40 cc of 0.5 mm diameter yttria-stabilized zirconia beads(available from Tosoh, Hudson, Ohio or from Toray Ceramics, GeorgeMissbach & Co., Atlanta, Ga.) were put into the basket of a HockmeyerHM-1/16 Micro Mill (“Hockmeyer mill”) (Hockmeyer Equipment Corp.,Harrison, N.J.). The desired MEK and dispersant (SOLSPERSE) were addedto the mill chamber and stirred with an air mixer for at least 4 minutesso as to dissolve the dispersant in the solvent. The diamond particleswere weighed into the chamber and the contents were stirred for anadditional minute to wet out the diamond particles. The resultingmixture was then milled at the maximum speed of the Hockmeyer thatavoided splashing. The resulting slurry was poured into a polyethylenecontainer and the solvent was allowed to evaporate until it could not bedetected by odor. Details of the compositions milled are shown below.

Diamond Particle Size Mill Charges (D₅₀) Mill Time Methyl EthylSOLSPERSE Diamond (micrometer) (min) Ketone (g) 24000 (g) Particles (g)0.25 20 280 54 900 0.50 15 280 27 900 1.00 10 255 16.5 1100

Glossary Name Description Source BYK 361 Polyacrylate copolymerBYK-Chemie USA, leveling agent Wallingford, CT 2,2′ Bypyridylethylenebis- A chelating agent Alfa Aesar, Ward Hill, MA salicylimine DP 1Diamond particles having a Tomei Diamond, D₅₀ of 0.25 μm and a D₅₀ ofEnglewood Cliffs, NJ 0.50 μm DP 2 Diamond particles having a NationalDiamond Research D₅₀ of other than 0.25 or Company, Chesterfield, MI0.50 μm Ethylene bis-salycimine A chelating agent Strem Chemicals,Newburyport, MA F180 SiC Silicon carbide particles Washington MillsElectro having a D₅₀ particle size of Mineral Corp., Niagara 80 μmFalls, NY GAFAC RE 610 (now An ionic dispersant Rhone-Poulenc, Granbury,RHODAFAC RE-610) NJ G Dia. (1.5) Diamonds, 1.5, 3.0, and 30 DiamondInnovation, G Dia. (3.0) μm diameter respectively Worthington, OH G Dia.(30) H Dia. (0.25) Diamonds, 0.25, 2-3, and Henan Hengxiang Diamond HDia. (2-3) 20-30 μm diameter Abrasive Company, H Dia. (20-30)respectively Zhengzhou, PR China GC 20000 Silicon carbide particlesFujimi Corporation, having a D₅₀ of 0.3 μm Nagoya, JP GC 8000 Siliconcarbide particles Fujimi Corporation having a D₅₀ of 1.0 μm GC 6000Silicon carbide particles Fujimi Corporation having a D₅₀ of 2.0 μm GC4000 Silicon carbide particles Fujimi Corporation having a D₅₀ of 3.0 μmGC 2000 Silicon carbide particles Fujimi Corporation having a D₅₀ of 9μm GC 1200 Silicon carbide particles Fujimi Corporation having a D₅₀ of13.5 μm GC 700 Silicon carbide particles Fujimi Corporation having a D₅₀of 18 μm GC 600 Silicon carbide particles Fujimi Corporation having aD₅₀ of 20 μm GC 400 Silicon carbide particles Fujimi Corporation havinga D₅₀ of 35 μm GC F320 Silicon carbide particles Fujimi Corporationhaving a D₅₀ of 29 μm HATCOL 1106 A polyol ester of HATCOL Corporation,dipentaerythritol and short Fords, NJ chain fatty acids (carrier oil)HATCOL 2300 A complexed polyol ester or HATCOL Corporationpentaerythritols and short chain fatty acids (carrier oil) HATCOL 2930 Adiester of trimellitic HATCOL Corporation anhydride and isodecyl alcohol(carrier oil) HATCOL 2949 A diester of dimer acid and HATCOL Corporation2-ethyhexyl alcohol (carrier oil) HATCOL 2999 A polyol ester or HATCOLCorporation pentaerythritol and short chain fatty acids (carrier oil)HATCOL 3165 A polyol ester of HATCOL Corporation dipentaerythritol andshort chain fatty acids (carrier oil) HATCOL 3371 A complexed polyolester of HATCOL Corporation trimethylol propane, adipic acid, caprylicacid, and capric acid (carrier oil) HATCOL 5150 A polyol ester of HATCOLCorporation dipentaerythritol and short chain fatty acids (carrier oil)HELOXY 71 An aliphatic epoxy ester Hexion Specialty resin (carrier oil)Chemicals, Inc., Houston, TX HELOXY 505 An aliphatic epoxy ester HexionSpecialty resin (carrier oil) Chemicals, Inc. IRGANOX 1010 AntioxidantCiba Specialty Chemicals, Tarrytown, NY KADOX 911 (0.1) Zinc Oxide, 0.1and 0.3 μm Horsehead Corporation, KADOX 930 (0.3) diameter respectivelyMonaca, PA Lithium Stearate A fatty acid salt (ionic Baerlocher USA,dispersant) Cincinnati, OH Nickel (<5) Spherical nickel powder, <5Novamet, Wykoff, New Nickel(−400 Mesh) μm diameter, and nickel Jerseypowder, <35 μm diameter respectively. OX-50 (0.04) Silica, 40 nanometersDegussa Corporation, diameter Parsippany, NJ PEG DistearatePoly(ethylene glycol) Aldrich Chemical Co., distearate having a numberMilwaukee, WI average molecular weight of about 930 (carrieroil/polymeric dispersant) RHODAFAC RE610 A polymeric dispersantRhone-Poulenc, Granbury, NJ SOLPLUS 520 A polymeric dispersant Noveon,Inc., a subsidiary of Lubrizol Corporation, Cleveland, OH SOLSPERSE16000 A polymeric dispersant Noveon, Inc. subsidiary of LubrizolCorporation, Cleveland, OH SOLSPERSE 24000 A polymeric dispersantNoveon, Inc. SOLSPERSE 39000 A polymeric dispersant Noveon, Inc. Sph. Al(3.0-4.5) Spherical aluminum Alfa Corp., Ward Hill, MA Sph. Al (17-30)powder, 3.0-4.5 and 17-30 μm diameter respectively T Dia. (0.25) 0.25 μmdiameter diamonds Tomei Corporation of America, Englewood Cliffs, NJTONE 305 A polyol resulting from the The Dow Chemical addition reactionof Company, Midland, MI caprolactone with trimethylol propane (carrieroil) Tungsten (1-5) Tungsten powder, 1-5 and Alfa Corp., Ward Hill,Tungsten (−325 Mesh) <50 μm diameter Massachusetts respectively. WA30000 Aluminum oxide particles Fujimi Corporation having a D₅₀ of 0.25μm WA6000 (2.0) Alumina grains, 2.0 μm Fujimi Corporation, diameterNagoya, Japan WA 4000 Aluminum oxide particles Fujimi Corporation havinga D₅₀ of 3.0 μm WA 500 Aluminum oxide particles Fujimi Corporationhaving a D₅₀ of 30 μm

“Sulfonated Bis(pentane dicaprolactone)”, an ionic dispersant, wasprepared as follows: To a reactor equipped with a mechanical stirrer,and vacuum was added 25 grams (0.476 equivalents) 1,5-pentane diol fromAldrich Chemical Co., Milwaukee, Wis., 54.3 grams (0.476 equivalents)caprolactone from Aldrich Chemical Co., and 8.0 grams (0.054equivalents) dimethyl-5-sodiosulfoisophthalate available from DuPontChemicals, Wilmington, Del. The reactor contents were stirred and heatedto 170° C. with a vacuum at 115 mm mercury. The reaction was completeafter 4 hours and a sample was analyzed by infrared spectroscopy. Thefinal product was a clear, low viscosity liquid with a theoreticalsulfonate equivalent weight of 1342.

“iC8 Modified silica nanoparticles”, a nonionic, inorganic dispersant,was prepared as follows: 61.42 grams BS1316 isooctyltrimethoxysilane(Wacker Silicones Corp., Adrian, Mich.), 1940 grams 1-methoxy-2-propanoland 1000 grams NALCO 2326 colloidal silica were combined in a 1 gallonglass jar. The mixture was shaken to ensure mixing and then placed in anoven at 80° C. overnight. The mixture was then dried in a flow throughoven at 150° C. to produce a white particulate solid.

“HIMOD”, a sulfonated polyol ionic dispersant, was prepared as follows:A reactor equipped with a mechanical stirrer, nitrogen purge, anddistillation apparatus was charged withdimethyl-5-sodiosulfoisophthalate (42.6 grams, 0.144 moles, availablefrom DuPont Chemicals, Wilmington, Del.), polyethylene glycol having amolecular weight of 400 (115.1 grams, 0.288 moles, available from UnionCarbide Chemical and Plastics Co., Inc. (now The Dow Chemical Company,Midland, Mich.)), and polypropylene glycol having a molecular weight of425 (122.3 grams, 0.288 moles, available from Aldrich Chemical Co.,Milwaukee, Wis.), and xylene (75 grams). The reactor was slowly heatedto 220° C. for about 1 hour to remove the xylene. Zinc acetate (0.2gram) was then added to the reactor and the temperature was held at 220°C. for 4 hours with concomitant distillation of methanol from thereaction. The temperature was reduced to about 160° C. and 0.2 Torr (SI)vacuum was applied to the resulting mixture for 30 minutes. The contentswere cooled to 120° C. under nitrogen to yield a clear, colorlesspolyol. The OH equivalent was determined to be 310 g/mole OH and thetheoretical sulfonated equivalent weight was found to be 1882 gramspolymer/mole sulfonated.

“TCPA HATCOL 3371”, an ionic dispersant was prepared as follows: To areactor equipped with a mechanical stirrer, and nitrogen purge was added45 grams (0.0241 equivalents) HATCOL 3371 and 3.4 grams (0.0121equivalents) tetrachlorophthalic anhydride. The reactor contents werestirred and heated to 150° C. with a constant nitrogen purge. Thereaction was complete after 4 hours and a sample was analyzed byinfrared spectroscopy. The final product was a brown, low viscosityliquid with a theoretical acid equivalent weight of 18,127.

“TONE 305 TCPA”, an ionic dispersant, was prepared as follows: To areactor equipped with a mechanical stirrer, and nitrogen purge was added10 grams (0.1 equivalents) Tone 305 from Dow Chemical Company, and 1.0grams (0.00355 equivalents) tetrachlorophthalic anhydride from AldrichChemical. The reactor contents were stirred and heated to 105° C. with aconstant nitrogen purge. The reaction was complete after 4 hours and asample was analyzed by infrared spectroscopy. The final product was aclear, low viscosity liquid with a theoretical acid equivalent weight of3,100.

Sample Preparation

Except as noted in specific Examples, dispersant or mixture ofdispersants was weighed into a watch glass. Any other surface activeingredients, if present, were also weighed onto the watch glass. Carrieroil(s), if present, was added to the dispersant(s) and the mixture wasstirred with a metal spatula until the dispersant(s) was fully mixedinto the carrier oil. Thermally conductive particles were added to thedispersant(s)/carrier oil mixture sequentially, starting with thesmallest particle size distribution. Each of the thermally conductiveparticle distributions was dispersed into the dispersant(s)/carrier oilmixture with a metal spatula before adding the next distribution ofthermally conductive particles. If necessary, the thermally conductivegrease composition was heated in an oven (110° C.) to reduce theviscosity of the composition to facilitate mixing of the thermallyconductive particles and/or subsequent additions of thermally conductiveparticles. The resultant thermally conductive greases were transferredinto and stored in capped glass vials.

In cases where the thermally conductive particles were pre-dispersed,the amount of dispersant to be carried on the fine thermally conductiveparticle distribution was calculated. The amount of remaining dispersantnecessary for the formulation was then determined and was weighed on toa watch glass. The remaining steps are identical to those describedabove.

Examples 1-64

The compositions of Examples 1-64 are shown in TABLE 1. The compositionsof Examples A-N and 65-74 are shown in TABLE 2. TABLE 3 shows dataresulting from the measurement of bulk conductivity and thermalimpedance for selected Examples. TABLE 4 shows viscosity data forselected Examples.

TABLE 1 Particle (g) Particle (g) Particle (g) Example Carrier Oil (g)Dispersant (g) Dispersant (g) (D₅₀, μm) (D₅₀, μm) (D₅₀, μm) Example 1HATCOL SOLSPERSE — GC GC GC 1106 39000 20000 4000 400 (0.32); (0.36)(2.12) (2.97) (3.92) HATCOL (0.3) (3.0) (35) 3371 (0.32) Example 2HATCOL SOLSPERSE — GC GC GC 1106 39000 20000 4000 400 (0.37); (0.36)(2.08) (2.97) (3.88) HATCOL (0.3) (3.0) (35) 3371 (0.37) Example 3HATCOL SOLSPERSE — GC GC GC 1106 39000 20000 4000 400 (0.42); (0.35)(2.07) (2.91) (3.84) HATCOL (0.3) (3.0) (35) 3371 (0.42) Example 4HATCOL SOLSPERSE — GC GC GC 3371 39000 20000 4000 400 (1.60) (0.90)(5.28) (7.40) (9.81) (0.3) (3.0) (35) Example 5 HATCOL SOLSPERSE — GC GCGC 3371 39000 20000 4000 400 (0.74) (0.36) (2.08) (2.93) (3.89) (0.3)(3.0) (35) Example 6 HATCOL SOLSPERSE — GC GC GC 3371 39000 20000 4000400 (0.85) (0.35) (2.07) (2.90) (3.82) (0.3) (3.0) (35) Example 7 —SOLSPERSE — GC GC GC 39000 20000 4000 400 (1.10) (2.09) (2.93) (3.90)(0.3) (3.0) (35) Example 8 HATCOL SOLSPERSE GAFAC RE 610 GC GC GC 110639000 (0.09) 20000 4000 400 (0.37); (0.27) (2.10) (2.93) (3.89) HATCOL(0.3) (3.0) (35) 3371 (0.37) Example 9 HATCOL SOLSPERSE HIMOD GC GC GC1106 39000 (0.09) 20000 4000 400 (0.37); (0.27) (2.09) (2.94) (3.88)HATCOL (0.3) (3.0) (35) 3371 (0.37) Example 10 HATCOL SOLSPERSE GAFAC RE610 GC GC GC 3371 39000 (0.18) 20000 4000 400 (0.75) (0.18) (2.10)(2.92) (3.87) (0.3) (3.0) (35) Example 11 HATCOL SOLSPERSE GAFAC RE 610GC GC GC 3371 39000 (0.09) 20000 4000 400 (0.74) (0.27) (2.09) (2.92)(3.89) (0.3) (3.0) (35) Example 12 HATCOL SOLSPERSE TCPA HATCOL 3371 GCGC GC 3371 39000 (0.27) 20000 4000 400 (0.57) (0.27) (2.09) (2.94)(3.90) (0.3) (3.0) (35) Example 13 HATCOL SOLSPERSE Lithium Stearate GCGC GC 1106 39000 (0.09) 20000 4000 400 (0.37); (0.27) (2.08) (2.93)(3.89) HATCOL (0.3) (3.0) (35) 3371 (0.37) Example 14 HATCOL SOLSPERSE2,2′ Bypyridylethylene GC GC GC 3371 39000 bis-salicylimine 20000 4000400 (0.15) (0.08) (0.02) (0.50) (0.70) (0.93) (0.3) (3.0) (35) Example15 HATCOL SOLSPERSE Ethylene bis-salycimine GC GC GC 3371 39000 (0.02)20000 4000 400 (0.15) (0.08) (0.49) (0.69) (0.92) (0.3) (3.0) (35)Example 16 HATCOL SOLSPERSE BYK 361 GC GC GC 3371 39000 (0.03) 200004000 400 (0.16) (0.09) (0.53) (0.74) (0.98) (0.3) (3.0) (35) Example 17HELOXY SOLSPERSE — GC GC GC 71 39000 20000 4000 400 (0.83) (0.27) (2.10)(2.92) (3.87) (0.3) (3.0) (35) Example 18 HELOXY SOLSPERSE — WA WA WA 7139000 30000 4000 500 (0.94) (0.26) (2.09) (3.00) (3.83) (0.25) (3.0)(30) Example 19 HATCOL SOLSPERSE — WA WA WA 3371 39000 30000 4000 500(0.94) (0.26) (2.07) (2.90) (3.83) (0.25) (3.0) (30) Example 20 TONE 305SOLSPERSE — GC GC GC (0.85) 39000 20000 4000 400 (0.35) (2.07) (2.90)(3.83) (0.3) (3.0) (35) Example 21 TONE 305 SOLSPERSE SulfonatedBis(pentane GC GC GC (0.75) 39000 dicaprolactone) 20000 4000 400 (0.27)(0.09) (2.09) (2.94) (3.88) (0.3) (3.0) (35) Example22 TONE 305SOLSPERSE TCPA modified TONE GC GC GC (0.85) 39000 305 20000 4000 400(0.26) (0.09) (2.07) (2.90) (3.83) (0.3) (3.0) (35) Example 23 TONE 305SOLSPERSE GAFAC RE 610 GC GC GC (0.85) 39000 (0.09) 20000 4000 400(0.26) (2.07) (2.91) (3.85) (0.3) (3.0) (35) Example 24 TONE 305SOLSPERSE — GC GC GC (0.75) 39000 20000 4000 400 (0.36) (2.08) (2.93)(3.88) (0.3) (3.0) (35) Example 25 HATCOL SOLSPERSE GAFAC RE 610 GC GCGC 3371 39000 (0.09) 20000 4000 400 (0.74) (0.27) (2.09) (2.94) (3.90)(0.3) (3.0) (35) Example 26 HATCOL SOLSPERSE GAFAC RE 610 GC GC GC 337139000 (0.09) 20000 4000 400 (0.74) (0.27) (2.09) (2.92) (3.89) (0.3)(3.0) (35) Example 27 HATCOL SOLSPERSE GAFAC RE 610 GC GC GC 3371 39000(0.09) 20000 4000 400 (0.74) (0.27) (2.09) (2.93) (3.88) (0.3) (3.0)(35) Example 28 HATCOL SOLSPERSE Sulfonated GC GC GC 3371 39000pentanediolcaprolactone 20000 4000 400 (0.74) (0.27) (0.09) (2.09)(2.93) (3.89) (0.3) (3.0) (35) Example 29 HATCOL SOLSPERSE — GC GC F1803371 39000 20000 2000 SiC (0.74) (0.36) (2.09) (2.93) (3.88) (0.3) (9.0)(80) Example 30 HATCOL SOLSPERSE — GC GC F180 1106 39000 20000 2000 SiC(0.74) (0.36) (2.10) (2.93) (3.89) (0.3) (9.0) (80) Example 31 HATCOLSOLSPERSE — GC GC F180 3371 39000 20000 2000 SiC (0.74) (0.36) (2.09)(2.94) (3.88) (0.3) (9.0) (80) Example 32 HATCOL SOLSPERSE GAFAC RE 610GC GC F180 3371 39000 (0.09) 20000 1200 SiC (0.74) (0.27) (2.09) (2.93)(3.89) (0.3) (13.5) (80) Example 33 HATCOL SOLSPERSE PEG Distearate GCGC F180 3371 39000 (0.09) 20000 2000 SiC (0.74) (0.27) (2.10) (2.93)(3.88) (0.3) (9.0) (80) Example 34 HATCOL SOLSPERSE iC8 Modified silicaGC GC F180 3371 39000 nanoparticles 20000 2000 SiC (0.74) (0.36) (0.01)(2.09) (2.93) (3.89) (0.3) (9.0) (80) Example 35 HATCOL SOLSPERSE GAFACRE 610 GC GC F180 1106 39000 (0.09) 20000 2000 SiC (0.74) (0.28) (2.09)(2.93) 3.88) (0.3) (9.0) (80) Example 36 — SOLSPERSE — DP 1 DP 2 DP 239000 (2.16) (3.03) (4.04) (0.80) (0.25) (3.0) (30) Example 37 HATCOLSOLSPERSE — DP 1 DP 2 DP 2 2300 39000 (2.19) (3.03) (4.02) (0.25) (0.55)(0.25) (3.0) (30) Example 38 HATCOL SOLSPERSE — DP 1 DP 2 DP 2 230039000 (2.14) (3.03) (4.03) (0.52) (0.28) (0.25) (3.0) (30) Example 39HATCOL SOLSPERSE — DP 1 DP 2 DP 2 2930 39000 (2.18) (3.05) (4.02) (0.52)(0.28) (0.25) (3.0) (30) Example 40 HATCOL SOLSPERSE — DP 1 DP 2 DP 23165 39000 (2.15) (3.04) (4.02) (0.52) (0.28) (0.25) (3.0) (30) Example41 HATCOL SOLSPERSE — DP 1 DP 2 DP 2 3371 39000 (2.18) (3.04) (4.02)(0.52) (0.28) (0.25) (3.0) (30) Example 42 HATCOL SOLSPERSE — GC GC GC3371 39000 20000 4000 400 (0.83) (0.27) (2.09) (2.92) (3.89) Example 43HELOXY SOLSPERSE — DP 1 DP 2 DP 2 71 39000 (2.10) (2.93) (3.89) (0.74)(0.36) (0.25) (6.0) (60) Example 44 (1) HELOXY SOLSPERSE — DP 2 DP 2 DP2 71 39000 (0.83) (1.43) (2.53) (0.52) (0.28) (0.1) (1.0) (9.0) Example45 HELOXY SOLSPERSE — DP 1 DP 2 DP 2 71 39000 (5.40) (7.58) (10.0)(1.08) (0.92) (0.25) (6.0) (60) Example 46 HATCOL SOLSPERSE — DP 1 DP 2DP 2 1106 24000 (3.55) (6.50) (11.0) (1.15) (0.13) (0.25) (3.0) (30)Example 47 (2) HATCOL SOLSPERSE — DP 1 DP 2 DP 2 1106 24000 (2.54)(4.66) (7.94) (0.51) (0.31) (0.25) (3.0) (30) Example 48 (2) HATCOLSOLSPERSE — DP 1 DP 2 DP 2 1106 24000 (2.53) (4.67) (7.96) (0.35) (0.46)(0.25) (3.0) (30) Example 49 HATCOL SOLSPERSE — DP 1 DP 2 DP 2 110639000 (2.39) (4.69) (7.94) (0.51) (0.46) (0.25) (3.0) (30) Example 50(2) HATCOL SOLSPERSE — DP 2 DP 2 DP 2 1106 24000 (2.14) (2.99) (3.97)(0.73) (0.21) (1.0) (6.0) (30) Example 51 (2) HELOXY SOLSPERSE — DP 2 DP2 DP 2 71 24000 (2.12) (2.96) (3.98) (0.74) (0.21) (1.0) (6.0) (30)Example 52 (2) HATCOL SOLSPERSE — DP 1 DP 2 DP 2 1106 24000 (2.10)(2.98) (4.00) (0.74) (0.25) (0.5) (6.0) (45) Example 53 (2) HELOXYSOLSPERSE — DP 1 DP 2 DP 2 71 24000 (2.10) (2.97) (3.98) (0.76) (0.24)(0.5) (6.0) (45) Example 54 (2) HELOXY SOLSPERSE — DP 1 DP 2 DP 2 7124000 (2.25) (3.08) (4.05) (0.63) (0.04) (0.25) (3.0) (30) Example 55HELOXY SOLSPERSE — DP 1 DP 2 DP 2 71 39000 (2.19) (3.06) (4.05) (0.64)(0.16) (0.25) (3.0) (30) Example 56 HELOXY SOLSPERSE — DP 1 DP 2 DP 2 7139000 (1.78) (3.04) (4.63) (0.45) (0.15) (0.25) (3.0) (30) Example 57HELOXY SOLSPERSE — DP 1 DP 2 DP 2 71 39000 (1.90) (3.02) (4.28) (0.55)(0.15) (0.25) (3.0) (30) Example 58 HATCOL SOLSPERSE — DP 1 DP 2 DP 22949 39000 (2.17) (3.02) (4.03) (0.64) (0.17) (0.25) (3.0) (30) Example59 HATCOL SOLSPERSE — DP 1 DP 2 DP 2 2300 39000 (2.19) (3.02) (4.02)(0.64) (0.17) (0.25) (3.0) (30) Example 60 HATCOL SOLSPERSE — DP 1 DP 2DP 2 2999 39000 (2.16) (3.04) (4.01) (0.64) (0.17) (0.25) (3.0) (30)Example 61 HATCOL SOLSPERSE — DP 1 DP 2 DP 2 5150 39000 (2.19) (3.03)(4.03) (0.64) (0.17) (0.25) (3.0) (30) Example 62 HELOXY SOLSPERSE — DP1 DP 2 DP 2 505 39000 (2.14) (3.03) (4.04) (0.63) (0.17) (0.25) (3.0)(30) Example 63 HELOXY SOLSPERSE — GC GC F180 71 39000 8000 2000 SiC(0.78) (0.17) (2.12) (2.98) (3.96) Example 64 HELOXY SOLSPERSE — DP 1 GCGC 71 39000 (1.91) 4000 700 (0.70) (0.20) (0.25) (2.67) (3.54) (1)Example 44 contained a 4^(th) thermally conductive particle: DP 2, (4.41grams), (60 μm). (2) Examples 46-48 and 50-54 used 0.25, 0.50, or 1.0 μmpre-dispersed diamond particles prepared according to the MillingProcedure and Sample Preparation described above.

Examples A-N and 65-74

Except as noted below, the components were individually weighed into awatch glass and mixed as follows. The silica, antioxidant, dispersants,and the carrier oil were initially combined with both the fine and themedium thermally conductive particles by stirring with a metal spatulauntil the combination of ingredients was a smooth and uniform blend. Thelargest particles were then added and the contents of the watch glasswere again stirred/kneaded with the metal spatula until the compositewas a smooth and uniform blend. If necessary, the thermally conductivegrease composition was heated in an oven (110° C.) to reduce theviscosity of the composition to facilitate mixing of the thermallyconductive particles and/or subsequent additions of thermally conductiveparticles. The resultant thermally conductive greases were transferredinto and stored in capped glass vials.

The preparation of certain samples was the same as above except thatabout 16.5 grams of a pre-blend of antioxidant, silica, dispersants, andcarrier fluid was prepared. The mixture was stirred with a metal spatulauntil the combination of ingredients was a smooth and uniform blend.Then on a clean watch glass about 0.824 gram of the pre-blend and boththe fine and the medium thermally conductive particles were combinedwith stirring, followed by the largest particles. The certain samplesand the pre-blend compositions are described below.

“Pre-blend A” Added to Blend “Pre-blend B” Added to Blend Component (g)Component (g) HATCOL 1106 9.10 HATCOL 1106 8.49 SOLSPERSE 5.50 SOLSPERSE5.52 39000 16000 RHODAFAC 1.83 RHODAFAC 1.84 RE610 RE610 IRGANOX 10100.0076 IRGANOX 1010 0.159 Colloidal Silica 0.025 Colloidal Silica 0.479Total Weight: 16.4626 Total Weight: 16.488Examples J, K, L, and I were prepared using Pre-blend A. Examples 65,67, and 71 and Examples M and N were prepared using Pre-blend B.

TABLE 2 Antioxidant (g) Particle (g) Particle (g) Particle (g) ExampleCarrier Oil (g) Dispersant (g) Dispersant (g) Silica (g) D₅₀ (μ) D₅₀ (μ)D₅₀ (μ) Example I HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX Sph. Al WA5001106 39000 RE-610 1010 911 (2.62) (5.24) (0.45) (0.27) (0.09) (0.0004)(1.31) (3-4.5) (30) OX-50 (0.1) (0.0013) Example J HATCOL SOLSPERSERHODAFAC IRGANOX KADOX Sph. Al GC F320 1106 39000 RE-610 1010 911 (2.62)(5.24) (0.45) (0.27) (0.09) (0.0004) (1.30) (3-4.5) (29) OX-50 (0.1)(0.0013) Example A HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX Sph. Al GC6001106 16000 RE-610 1010 911 (2.62) (5.24) (0.42) (0.27) (0.09) (0.0075)(1.31) (3-4.5) (20) OX-50 (0.1) (0.024) Example B HATCOL SOLSPERSERHODAFAC IRGANOX KADOX Sph. Al GC600 1106 16000 RE-610 1010 930 (2.62)(5.24) (0.42) (0.27) (0.09) (0.0081) (1.31) (3-4.5) (20) OX-50 (0.3)(0.028) Example C HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX Sph. Al GC6001106 16000 RE-610 1010 930 (2.59) (5.18) (0.52) (0.27) (0.09) (0.0077)(1.29) (3-4.5) (20) OX-50 (0.3) (0.027) Example 65 HATCOL SOLSPERSERHODAFAC IRGANOX KADOX WA6000 Sph. Al 1106 16000 RE-610 1010 911 (2.62)(5.24) (0.42) (0.27) (0.09) (0.0080) (1.31) (2.0) (17-30) OX-50 (0.1)(0.024) Example 66 HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX GC6000 Sph.Al 1106 16000 RE-610 1010 930 (2.59) (5.18) (0.52) (0.27) (0.09)(0.0090) (1.29) (2.0) (17-30) OX-50 (0.3) (0.027) Example 67 HATCOLSOLSPERSE RHODAFAC IRGANOX KADOX GC6000 Sph. Al 1106 16000 RE-610 1010911 (2.62) (5.24) (0.42) (0.27) (0.09) (0.0079) (1.31)) (2.0) (17-30)OX-50 (0.1) (0.023) Example K HATCOL SOLSPERSE RHODAFAC IRGANOX T Dia. GDia, G Dia. 1106 39000 RE-610 1010 (1.30) (2.62) (5.24) (0.45) (0.27)(0.09) (0.0004) (0.25) (3.0) (30) OX-50 (0.0013) Example D HATCOLSOLSPERSE RHODAFAC IRGANOX T Dia. G Dia. G Dia. 1106 16000 RE-610 1010(1.31) (2.62) (5.24) (0.42) (0.27) (0.09) (0.0087) (0.25) (3.0) (30)OX-50 (0.024) Example E HATCOL SOLSPERSE RHODAFAC IRGANOX H Dia. H Dia.H Dia. 1106 16000 RE-610 1010 (1.31) (2.62) (5.24) (0.42) (0.27) (0.09)(0.0077) (0.25) (2-3) (20-30) OX-50 (0.026) Example 68 HATCOL SOLSPERSERHODAFAC IRGANOX KADOX G Dia. Sph. Al 1106 16000 RE-610 1010 911 (2.62)(5.24) (0.42) (0.27) (0.09) (0.0080) (1.31) (1.5) (3-4.5) OX-50 (0.1)(0.022) Example 69 HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX G Dia. Sph.Al 1106 16000 RE-610 1010 930 (2.62) (5.24) (0.42) (0.27) (0.09)(0.0076) (1.31) (3.0) (17-30) OX-50 (0.3) (0.022) Example 70 HATCOLSOLSPERSE RHODAFAC IRGANOX KADOX G Dia. Sph. Al 1106 16000 RE-610 1010911 (2.62) (5.24) (0.42) (0.27) (0.09) (0.0092) (1.31) (1.5) (17-30)OX-50 (0.1) (0.023) Example 71 HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX HDia. Sph. Al 1106 16000 RE-610 1010 911 (2.62) (5.24) (0.42) (0.27)(0.09) (0.0079) (1.31) (2-3) (17-30) OX-50 (0.1) (0.023) Example MHATCOL SOLSPERSE RHODAFAC IRGANOX KADOX H Dia. H Dia. 1106 16000 RE-6101010 911 (2.62) (5.24) (0.42) (0.27) (0.09) (0.0080) (1.30) (2-3)(20-30) OX-50 (0.1) (0.024) Example L HATCOL SOLSPERSE RHODAFAC IRGANOXKADOX Sph. Al G Dia. 1106 39000 RE-610 1010 911 (2.62) (5.24) (0.45)(0.27) (0.09) (0.0004) (1.31) (3-4.5) (30) OX-50 (0.1) (0.0013) ExampleN HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX Sph. Al H Dia. 1106 16000RE-610 1010 911 (2.62) (5.24) (0.45) (0.27) (0.09) (0.0004) (1.31)(3-4.5) (20-30) OX-50 (0.1) (0.024) Example 72 HATCOL SOLSPERSE RHODAFACIRGANOX KADOX G Dia. Nickel 1106 16000 RE-610 1010 911 (1.18) (7.64)(0.35) (0.17) (0.06) (0.0066) (0.583) (3.0) (-400 OX-50 (0.1) Mesh)(0.018) Example 73 HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX GC4000Tungsten 1106 16000 RE-610 1010 911 (0.572) (8.81) (0.16) (0.09) (0.04)(0.0027) (0.310) (3.0) (-325 OX-50 (0.1) Mesh) (0.0085) Example 74HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX G Dia. Tungsten 1106 16000RE-610 1010 911 (0.62) (8.77) (0.16) (0.09) (0.04) (0.0042) (0.300)(3.0) (-325 OX-50 (0.1) Mesh) (0.010) Example F HATCOL SOLSPERSERHODAFAC IRGANOX KADOX Sph. H Dia. 1106 16000 RE-610 1010 911 Nickel(4.23) (0.42) (0.28) (0.09) (0.0077) (0.789) (4.16) (20-30) OX-50 (0.1)(<5) (0.024) Example G HATCOL SOLSPERSE RHODAFAC IRGANOX KADOX TungstenGC600 1106 16000 RE-610 1010 911 (6.24) (2.66) (0.29) (0.19) (0.06)(0.0070) (0.538) (1-5) (20) OX-50 (0.1) (0.015) Example H HATCOLSOLSPERSE RHODAFAC IRGANOX KADOX Tungsten H Dia. 1106 16000 RE-610 1010911 (6.07) (2.84) (0.28) (0.19) (0.06) (0.0048) (0.539) (1-5) (20-30)OX-50 (0.1) (0.015)

TABLE 3 Thermal Impedance at Bulk Conductivity 100 μm meter bar gapExample (W/m-K) (° C.-cm²/W) 1 3.71 0.497 2 3.50 0.542 3 2.86 0.555 44.18 0.518 5 3.53 0.476 6 3.21 0.602 7 4.19 0.355 8 3.74 0.520 9 3.420.548 10 3.84 0.431 11 4.24 0.444 12 3.52 0.425 13 3.71 0.528 14 3.780.464 15 3.77 0.532 16 3.58 0.555 17 4.24 0.644 18 3.86 0.547 19 3.150.482 20 3.54 0.616 21 3.62 0.622 22 4.10 0.608 23 3.71 0.638 24 3.910.580 25 3.95 0.545 26 3.93 0.63 27 3.44 0.605 28 3.44 0.604 29 4.450.652 30 3.49 0.628 31 3.84 0.625 32 3.65 0.582 33 3.28 0.507 34 3.010.569 35 3.63 0.595 36 5.01 0.409 37 4.92 0.389 38 4.58 0.451 39 3.710.464 40 4.47 0.514 41 4.23 0.451 42 2.73 0.412 43 3.52 0.662 44 5.880.491 45 5.62 0.519 46 4.35 0.473 47 6.31 0.421 48 6.80 0.388 49 6.120.395 50 3.18 0.821 51 3.33 0.728 52 2.78 0.871 53 2.96 0.839 54 4.110.535 55 4.00 0.403 56 5.22 0.351 57 4.92 0.372 58 2.44 0.398 59 3.350.514 60 3.62 0.562 61 3.56 0.596 62 4.18 0.501 63 4.24 0.644 64 2.730.412 Example I 3.94 0.374 Example J 4.78 0.275 Example A 4.64 0.327Example B 4.59 0.336 Example C 3.80 0.411 Example 65 4.81 0.323 Example66 5.06 0.310 Example 67 6.12 0.261 Example K 4.96 0.277 Example D 5.050.315 Example E 4.61 0.322 Example 68 5.50 0.280 Example 69 5.31 0.306Example 70 5.27 0.263 Example 71 5.16 0.288 Example 72 3.30 0.395Example 73 4.32 0.404 Example 74 3.94 0.404 Example M 5.08 0.304 ExampleL 4.27 0.346 Example N 4.88 0.325 Example F 3.23 0.377 Example G 3.240.405 Example H 3.40 0.405 CE 1 2.49 0.766 CE 2 2.54 0.665 CE 3 3.440.383 CE 4 3.39 0.344 CE 1 = ShinEtsu G751, Sample 1 CE 2 = ShinEtsuG751, Sample 2 CE 3 = Dow Corning TC5022 CE 4 = ShinEtsu G751, Sample 3

TABLE 4 0.25 & 0.5 mm 0.5 mm Gap Gap Ave. 0.25 mm Gap η (mPa · s) η (mPa· s) η (mPa · s) @ 25° C. @ 125° C. @ 125° C. & 1.25/sec & 1.25/sec &1.25/sec Example Shear Rate Shear Rate Shear Rate 26 — 4.4E+04 5.8E+0428 — 1.1E+06 1.0E+06 30 2.7E+06 — 1.3E+04 31 — 9.2E+04 7.9E+04 32 —2.5E+04 3.8E+04 35 — — 1.7E+04 43 — 4.2E+04 2.9E+04 44 — — 2.4E+05 454.4E+06 — — CE 1.2E+06 4.3E+05 3.1E+05 CE = ShinEtsu G751

Foreseeable modifications and alterations of this invention will beapparent to those skilled in the art without departing from the scopeand spirit of this invention. This invention should not be restricted tothe embodiments that are set forth in this application for illustrativepurposes.

1. A method of making a thermally conductive grease comprising the stepsof: providing a carrier oil, at least one polymeric dispersant, andthermally conductive particles in an amount comprising between 0 toabout 49.5 weight percent of carrier oil; about 0.5 to about 5 weightpercent of the at least one polymeric dispersant; and at least about49.5 weight percent of thermally conductive particles, wherein thethermally conductive particles comprise at least three distributions ofthermally conductive particles, each of the at least three distributionsof thermally conductive particles having an average (D₅₀) particle sizewhich differs from the other distributions by at least a factor of 5;mixing the carrier oil and polymeric dispersant together to form amixture; and mixing the thermally conductive particles sequentially,finest to largest average particle size, into the carrier oil andpolymeric dispersant mixture to obtain a thermally conductive greasehaving a bulk thermal conductivity of from about 2 to about 7 W/m-° K.and a viscosity measured at 25° C. of at least about 10⁶ mPas.
 2. Themethod of claim 1 wherein the thermally conductive particles arepretreated with a dispersant prior to mixing the thermally conductiveparticles into the mixture of carrier oil and polymeric dispersant.
 3. Amicroelectronic package comprising: a substrate; at least onemicroelectronic heat source attached to the substrate; and the thermallyconductive grease made according to claim 1 on the at least onemicroelectronic heat source.
 4. The microelectronic package of claim 3further comprising a heat spreader and the thermally conductive greaseis between the microelectronic heat source and the heat spreader.
 5. Themicroelectronic package of claim 4 further comprising a heat dissipationdevice wherein thermally conductive grease is between the heat spreaderand the heat dissipation device.
 6. A method of making a thermallyconductive grease comprising the steps of: providing a carrier oil, atleast one polymeric dispersant, and thermally conductive particles in anamount comprising between 0 to about 49.5 weight percent of carrier oil;about 0.5 to about 5 weight percent of the at least one polymericdispersant; and at least about 49.5 weight percent of thermallyconductive particles, wherein the thermally conductive particlescomprise at least three distributions of thermally conductive particles,each of the at least three distributions of thermally conductiveparticles having an average (D₅₀) particle size which differs from theother distributions by at least a factor of 5; mixing the thermallyconductive particles together to form a mixture of thermally conductiveparticles; mixing the carrier oil and the polymeric dispersant togetherto form a mixture of carrier oil and polymeric dispersant; and mixingthe mixture of thermally conductive particles with the mixture ofcarrier oil and polymeric dispersant.
 7. The method of claim 6 whereinthe thermally conductive particles are pretreated with a dispersantprior to mixing the mixture of thermally conductive particles into themixture of carrier oil and polymeric dispersant.
 8. A microelectronicpackage comprising: a substrate; at least one microelectronic heatsource attached to the substrate; and the thermally conductive greasemade according to claim 6 on the at least one microelectronic heatsource.
 9. The microelectronic package of claim 8 further comprising aheat spreader and the thermally conductive grease is between themicroelectronic heat source and the heat spreader.
 10. Themicroelectronic package of claim 9 further comprising a heat dissipationdevice wherein thermally conductive grease is between the heat spreaderand the heat dissipation device.